Ok the result is in.
Test board was a Carbon Art 66 at 111L and 2450 L
Back seat with head rest removed laid flat, front seat with head rest removed, push all the way forward then lay flat. The two seats will
almost fit together and create a flat surface. If I had to do this all the time I'd modify the seat to go another 100mm further forward.
The board then slid under the glove box area....just..... and I could shut the rear door. The front door was a bit of an issue as the arm rest was hard against the board when closed and very close to the gear shift lever. I could select 1st but second was tight. A narrower board would make this easier.
I tried a 460 mast but it would only fit resting on the dash. Nothing a strap wouldn't fix to hold it in place

. No chance getting the 520 mast in. The rest of the gear no problems but you run out of room very quickly so its a 1 board, 1 boom, 1 sail type car. This is why I have a 4.5mt trailer

If it was my only choice of transport and I was going to do this all the time I'd buy a set of racks. For the very odd sail not an issue and I now know that I can pinch my wife's car for a sail
